Hyperbranched polymers and multiarm star polymers are a type of dendritic polymers which have attracted substantial interest during the last 30 years because of their unique properties. They can be used to modify epoxy thermosets to... more
Hyperbranched polymers and multiarm star polymers are a type of dendritic polymers which have attracted substantial interest during the last 30 years because of their unique properties. They can be used to modify epoxy thermosets to increase their toughness and flexibility but without adversely affecting other properties such as reactivity or thermal properties. In addition, the final properties of materials can be tailored by modifying the structure, molecular weight, or type of functional end-groups of the hyperbranched and multiarm star polymers. In this review, we focus on the modification of epoxy-based thermosets with hyperbranched and multiarm star polymers in terms of the effect on the curing process of epoxy formulations, thermal, mechanical, and rheological properties, and their advantages in fire retardancy on the final thermosets.
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In this work, a new family of poly(thiourethane) shape memory thermosetting actuators was developed and characterized. These materials can be easily prepared from mixtures of two different aliphatic diisocyanates and a trithiol in the... more
In this work, a new family of poly(thiourethane) shape memory thermosetting actuators was developed and characterized. These materials can be easily prepared from mixtures of two different aliphatic diisocyanates and a trithiol in the presence of a latent catalyst, allowing an easy manipulation of the formulation. Rheological studies of the curing process confirm the latent character of the formulations. The glass transition temperatures and the mechanical properties can be modified by varying the proportion of diisocyanates (hexamethylene diisocyanate, HDI, and isophorone diisocyanate, IPDI) with stoichiometric amounts of trimethylolpropane tris(3-mercaptopropionate). The shape-memory behavior was deeply investigated under three different conditions: unconstrained, partially constrained, and fully constrained. Tests were performed in single cantilever bending mode to simulate conditions closer to real complex mechanics of thermomechanical actuators under flexural performances. The ...
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Click chemistry has emerged as an effective polymerization method to obtain thermosets with enhanced properties for advanced applications. In this article, commonly used click reactions have been reviewed, highlighting their advantages in... more
Click chemistry has emerged as an effective polymerization method to obtain thermosets with enhanced properties for advanced applications. In this article, commonly used click reactions have been reviewed, highlighting their advantages in obtaining homogeneous polymer networks. The basic concepts necessary to understand network formation via click reactions, together with their main characteristics, are explained comprehensively. Some of the advanced applications of thermosets obtained by this methodology are also reviewed.
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Epoxy resins are commonly used as thermosetting materials due to their excellent mechanical properties, high adhesion to many substrates and good heat and chemical resistances. This type of thermosets is intensively used in a wide range... more
Epoxy resins are commonly used as thermosetting materials due to their excellent mechanical properties, high adhesion to many substrates and good heat and chemical resistances. This type of thermosets is intensively used in a wide range of fields, where they act as fiber-reinforced materials, general-purpose adhesives, high-performance coatings and encapsulating materials. These materials are formed by the chemical reaction of multifunctional epoxy monomers forming a polymer network produced through an irreversible way. In this article the improvement of the characteristics of epoxy thermosets using different hyperbranched poly(ethyleneimine) (PEI) derivatives will be explained.
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Novel composite coatings prepared from 3,4-epoxy cyclohexylmethyl 3,4-epoxycyclohexane carboxylate (ECC) and different ceramic fillers have been prepared to improve the thermal dissipation of electronic devices. As latent cationic... more
Novel composite coatings prepared from 3,4-epoxy cyclohexylmethyl 3,4-epoxycyclohexane carboxylate (ECC) and different ceramic fillers have been prepared to improve the thermal dissipation of electronic devices. As latent cationic initiator, a benzylanilinium salt with triethanolamine has been used, which leads to a polyether matrix. Different proportions of Al2O3, AlN and SiC as fillers were added to the reactive formulation. The effect of the fillers selected and their proportions on the evolution of the curing was studied by calorimetry and rheometry. The thermal conductivity, thermal stability, thermal expansion coefficient and thermomechanical and mechanical properties of the composites were evaluated. An improvement of 820% in thermal conductivity in reference to the neat material was reached with a 75 wt % of AlN, whereas glass transition temperatures higher than 200 °C were determined in all the composites.
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Research Interests: Materials Engineering, Chemical Engineering, Materials Science, Analytical Chemistry, Polymer Chemistry, and 14 moreCatalysis, Polymer, Differential scanning calorimetry, Cationic polymerization, Epoxy, Epoxy Resins, Glass Transition, Thermal Analysis, Thermal Stability, Thermogravimetric Analysis, Eugenol, Squalene, Click, and Thermosets
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Photoinitiated thiol-yne reaction was combined with thermal thiol-epoxy to get thermosets by dual curing from propargyl decorated poly(ethyleneimine) and DGEBA.
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A new dual curing procedure based in the combination of UV-induced thiol-ene and thermal thiol-epoxy reactions has been established by the use of a latent amine precursor that can catalyze the thermal process.
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Mixtures of DGEBA with γ-valerolactone (γ-VL) or α-methyl-γ-butyrolactone (γ-MBL) 2:1 (mol/mol) were cationically copolymerized in the presence of scandium, ytterbium, or lanthanum triflates as initiators. The evolution of the different... more
Mixtures of DGEBA with γ-valerolactone (γ-VL) or α-methyl-γ-butyrolactone (γ-MBL) 2:1 (mol/mol) were cationically copolymerized in the presence of scandium, ytterbium, or lanthanum triflates as initiators. The evolution of the different reactive groups was followed by means of FTIR/ATR spectroscopy. From these experiments, we could detect the coexistence of two unexpected processes: a reversion of the intermediate spiroorthoester formed to the initial products and a depolymerization process, which only takes place in samples with γ-VL, when scandium triflate was used as initiator or when the proportion of ytterbium triflate was increased from 1 to 3 phr. When γ-MBL was used as comonomer no depolymerization occurs which supports the proposed mechanism. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 2129–2141, 2007
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Research Interests: Engineering, Materials Science, Polymer Chemistry, Kinetics, FTIR, and 14 moreDifferential scanning calorimetry, bisphenol A, Applied, Cationic polymerization, Crosslinking, Epoxy, CHEMICAL SCIENCES, Thermal Stability, Thermogravimetric Analysis, Ether, Shrinkage, Reaction Mechanism, Journal of Applied Polymer Science, and Thermosets
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Cellulose nanocrystals (CNCs) are attractive materials due to their renewable nature, high surface-to-volume ratio, crystallinity, biodegradability, anisotropic performance, or available hydroxyl groups. However, their source and... more
Cellulose nanocrystals (CNCs) are attractive materials due to their renewable nature, high surface-to-volume ratio, crystallinity, biodegradability, anisotropic performance, or available hydroxyl groups. However, their source and obtaining pathway determine their subsequent performance. This work evaluates cellulose nanocrystals (CNCs) obtained from four different eucalyptus species by acid hydrolysis, i.e., E. benthamii, E. globulus, E. smithii, and the hybrid En × Eg. During preparation, CNCs incorporated sulphate groups to their structures, which highlighted dissimilar reactivities, as given by the calculated sulphate index (0.21, 0.97, 0.73 and 0.85, respectively). Although the impact of the incorporation of sulphate groups on the crystalline structure was committed, changes in the hydrophilicity and water retention ability or thermal stability were observed. These effects were also corroborated by the apparent activation energy during thermal decomposition obtained through kine...
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Dual-curing thermosetting systems are recently being developed as an alternative to conventional curing systems due to their processing flexibility and the possibility of enhancing the properties of cured parts in single- or multi-stage... more
Dual-curing thermosetting systems are recently being developed as an alternative to conventional curing systems due to their processing flexibility and the possibility of enhancing the properties of cured parts in single- or multi-stage processing scenarios. Most dual-curing systems currently employed in three-dimensional (3D) printing technologies are aimed at improving the quality and properties of the printed parts. However, further benefit can be obtained from control in the curing sequence, making it possible to obtain partially reacted 3D-printed parts with tailored structure and properties, and to complete the reaction by activation of a second polymerization reaction in a subsequent processing stage. This paves the way for a range of novel applications based on the controlled reactivity and functionality of this intermediate material and the final consolidation of the 3D-printed part after this second processing stage. In this review, different strategies and the latest deve...
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A new type of tetraphenylborate salts derived from highly basic and nucleophilic amines, namely 1,5-diazabicyclo[4.3.0]non-5-ene (DBN), 1,8-diazabicyclo(5.4.0)undec-7-ene (DBU) and triazabicyclodecene (TBD), was applied to the preparation... more
A new type of tetraphenylborate salts derived from highly basic and nucleophilic amines, namely 1,5-diazabicyclo[4.3.0]non-5-ene (DBN), 1,8-diazabicyclo(5.4.0)undec-7-ene (DBU) and triazabicyclodecene (TBD), was applied to the preparation of networked poly(thiourethane)s (PTUs), which showed a vitrimer-like behavior, with higher stress-relaxation rates than PTUs prepared by using dibutyl thin dilaurate (DBTDL) as the catalyst. The use of these salts, which release the amines when heated, instead of the pure amines, allows the formulation to be easily manipulated to prepare any type of samples. The materials prepared from stoichiometric mixtures of hexamethylene diisocyanate (HDI), trithiol (S3) and with a 10% of molar excess of isocyanate or thiol were characterized by FTIR, thermomechanical analysis, thermogravimetry, stress-relaxation tests and tensile tests, thus obtaining a complete thermal and mechanical characterization of the materials. The recycled materials obtained by grin...
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A series of bio-based epoxy shape-memory thermosetting polymers were synthesized starting from a triglycidyl phloroglucinol (3EPOPh) and trimethylolpropane triglycidyl ether (TPTE) as epoxy monomers and a polyetheramine (JEF) as... more
A series of bio-based epoxy shape-memory thermosetting polymers were synthesized starting from a triglycidyl phloroglucinol (3EPOPh) and trimethylolpropane triglycidyl ether (TPTE) as epoxy monomers and a polyetheramine (JEF) as crosslinking agent. The evolution of the curing process was studied by differential scanning calorimetry (DSC) and the materials obtained were characterized by means of DSC, thermogravimetric analysis (TGA), dynamic mechanical analysis (DMA), stress-strain tests, and microindentation. Shape-memory properties were evaluated under free and totally constrained conditions. All results were compared with an industrial epoxy thermoset prepared from standard diglycidyl ether of Bisphenol A (DGEBA). Results revealed that materials prepared from 3EPOPh were more reactive and showed a tighter network with higher crosslinking density and glass transition temperatures than the prepared from DGEBA. The partial substitution of 3EPOPh by TPTE as epoxy comonomer caused an i...
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The pure trifunctional glycidyl monomer from phloroglucinol (3EPO-Ph) was synthesized and used as feedstock in the preparation of novel bio-based thermosets by thiol-epoxy curing. The monomer was crosslinked with different commercially... more
The pure trifunctional glycidyl monomer from phloroglucinol (3EPO-Ph) was synthesized and used as feedstock in the preparation of novel bio-based thermosets by thiol-epoxy curing. The monomer was crosslinked with different commercially available thiols: tetrafunctional thiol (PETMP), trifunctional thiol (TTMP) and an aromatic dithiol (TBBT) as curing agents in the presence of a base. As catalyst, two different commercial catalysts: LC-80 and 4-(N,N-dimethylamino) pyridine (DMAP) and a synthetic catalyst, imidazolium tetraphenylborate (base generator, BG) were employed. The curing of the reactive mixtures was studied by using DSC and the obtained materials by means of differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and dynamic mechanical thermal analysis (DMTA). The results revealed that only the formulations catalyzed by BG showed a latent character. Already prepared thermosetting materials showed excellent thermal, thermomechanical and mechanical propertie...
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New thermosets from a triglycidyl eugenol derivative (3EPOEU) as a renewable epoxy monomer were obtained by an epoxy-amine curing process. A commercially-available Jeffamine® and isophorone diamine, both obtained from renewable resources,... more
New thermosets from a triglycidyl eugenol derivative (3EPOEU) as a renewable epoxy monomer were obtained by an epoxy-amine curing process. A commercially-available Jeffamine® and isophorone diamine, both obtained from renewable resources, were used as crosslinking agents, and the materials obtained were compared with those obtained from a standard diglycidylether of bisphenol A (DGEBA). The evolution of the curing process was studied by differential scanning calorimetry and the materials obtained were characterized by means of calorimetry, thermogravimetry, thermodynamomechanical analysis, stress–strain tests and microindentation. 3EPOEU formulations were slightly less reactive, and the thermosets obtained showed higher Tgs than those prepared from DGEBA, since they had higher crosslinking density than formulations with DGEBA because of the more compact structure and higher functionality of the eugenol derivative. 3EPOEU thermosets showed good thermal stability and mechanical proper...
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ABSTRACT Hybrid thiol-ene system based on a hyperbranched polyester with different degrees of 10-undecenoyl modification are prepared via a dual UV-thermal process. The pristine thiol-ene formulation shows a high reactivity towards UV... more
ABSTRACT Hybrid thiol-ene system based on a hyperbranched polyester with different degrees of 10-undecenoyl modification are prepared via a dual UV-thermal process. The pristine thiol-ene formulation shows a high reactivity towards UV curing and the addition of the inorganic precursor to the photocurable formulation does not affect the UV-curing process. The crosslinked systems show an increase of Tg by increasing the vinyl functionality content in the HBP and a Tg increase is also evidenced in the hybrid system as a function of inorganic precursor content. Morphological investigations show that the inorganic domains generated in situ are homogeneously distributed throughout the polymeric matrix. By varying the 10-undecenoyl modification in the terminal groups of the HBP, the size of the inorganic domains is tunable and it is possible to decrease the dimension of the silica domains by using the HBP with a higher modification degree.
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Diglycidylether of bisphenol A (DGEBA) was cured with different proportions of 1,6-dioxaspiro[4.4]nonane-2,7-dione (s(γ-BL)) with ytterbium triflate as initiator. The curing was studied with differential scanning calorimetry (DSC) and... more
Diglycidylether of bisphenol A (DGEBA) was cured with different proportions of 1,6-dioxaspiro[4.4]nonane-2,7-dione (s(γ-BL)) with ytterbium triflate as initiator. The curing was studied with differential scanning calorimetry (DSC) and Fourier transform infrared in the attenuated total reflection mode (FTIR/ATR). FTIR/ATR was used to monitor the competitive reactive processes and to quantify the conversion of the epoxide, lactone and intermediate spiroorthoester (SOE)
Research Interests: Engineering, Kinetics, Polymer, Differential scanning calorimetry, bisphenol A, and 8 moreCHEMICAL SCIENCES, Glass Transition Temperature, Fourier transform infrared spectroscopy, Dynamic Mechanical Thermal Analysis (DMTA), Shrinkage, Fourier transform infrared, Mechanical Property, and Thermal Degradation
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